1. Field of the Invention
This invention relates to an apparatus for tightening or loosening a screw member to be used for fastening a form for molding concrete secondary products.
2. Description of the Prior Art
As a centrifugal-type molding form for concrete secondary products, as described in the Official Gazette of Japanese Patent Appln. Publication No. 59-49169, there are used a pair of halved bodies, each having a semi-circular sectional shape with a flange at each of facing side portions. Both the halved bodies are fastened with a screw member consisting of a bolt, a nut or the like disposed at each of a plurality of portions on the flange.
One of tightening/loosening apparatuses used for a screw member to assemble or disassemble such a form is described in the above-mentioned Official Gazette. In the known tightening/loosening apparatus, while a form disposing the screw members thereon is continuously moved in one direction and while a plurality of tightening and loosening mechanisms, i.e., processing mechanisms are moved together with the form, each screw member is rotated by means of a wrench of each processing mechanism. The processing mechanisms are advanced one after another with the movement of the form, and are returned to their initial positions after tightening or loosening the screw members. Incidentally, the direction of the movement of the form is defined as the forward and backward direction, and the horizontal direction to cross approximately at right angles a passage for the form is defined as the lateral direction.
While the corresponding processing mechanism is moved together with the form, each wrench is moved by a moving mechanism toward the screw member of the form to be engaged therewith, and the screw member is tightened or loosened by the wrench. Thereafter, each wrench is moved to be away from the screw member by the moving mechanism to be disengaged from the screw member.
In the known tightening/loosening apparatus, however, when the wrench becomes unmovable relative to the screw member while engaged with the screw member due to some trouble in the moving mechanism or the like, even if the processing mechanisms have been moved to predetermined positions for disengaging the wrench from the screw member, the wrench is farther moved with the form in the moving direction of the form without being released or disengaged from the screw member. As a result, the screw member, form, wrench, wrench moving means or the like are broken and scattered, which causes dangers.